This invention relates to a device for guiding laminar elements for processing, particularly intended for machines operative to fold up hides and synthetic materials, such as shoe uppers and insoles, leather articles.
It is known that hides and comparable laminar elements are in many cases to be folded and set in the folded position to provide folded over and well finished edges, for example. Particularly in the shoemaking industrywidely used and important are folding machines referred to as "thermocement folding machines" which work on hides and the like, as pre-arranged with fleshed and thinned edges, and are operative to both spread an adequate adhesive and to fold over and press the edges. The hide or the like is fed in an upside down position under members which dispense glue drops or beads onto the flat areas of the overturned hide onto which the folded over edges are then pressed and caused to adhere. The glue employed is a hot-melt type and is delivered through a line which extends as far as the bottom end of the so-called "shoe", formed by a rigid lug which shaves by its end the area of the hide or the like to be glued. Beneath the hide being processed, and aligned to the cited shoe, there is provided a "jaw" or movable clamping body which moves up periodically to clamp the hide or the like against said shoe. With the hide released, the same is advanced by an advance mechanism having two oscillating elements called the "anvil" and "hammer" which grab intermittently the hide and pull through a predetermined pitch distance. As soon as said anvil and hammer leave the hide the latter is clamped between said shoe and jaw. The edge upturning is effected by first pressing the hide or the like onto a guide having the shape of a small block with an arcuate face facing the cited shoe. The guide or small block causes initial raising and bending of the edges and the final fold is obtained by the pressing action applied by the anvil and hammer, which cause the folded over edges to adhere to the dispensed glue.
To facilitate the edge folding, especially in sharply bent areas, the folding machines also include severing members which subdivide the folded over edge into several small portions independent of one another.
On the work surface there are also provided various photocells which sense the shape of the workpiece and adjust accordingly the transport speed of the material being processed and the distance between the various edge cuts, which cuts are to be made the closer the sharper is the bend in the workpiece.
An essential condition to the proper operation of these machines is a correct position of the hide or synthetic material being processed at the cited small block.
This correct position may be either achieved in a substantially manual way, such as under the supervision and action of an operator, or in an automatic way, by means of purposely provided guiding devices.
Heretofore, manual and direct supervision of the process by an operator has been dominant over automatic monitoring, because the guiding devices provided heretofore have proved in many cases inadequate.
By way of example mention may be made of Italian patent No. 685886, and corresponding U.S. Pat. No. 3088144, wherein a device for guiding hides and the like is described which is based on the use of an advance wheel which operates uninterruptedly on the material being processed. The technical solution just mentioned, like all those based on roller guide or in any case geometrically well-defined elements, have the fundamental drawback of operating in an inflexible manner, that is to say, by applying a constant action which tends to move the hide or the like in a tightly constrained manner.
In this situation the guiding devices are to adjusted very accurately and yet they easily prove inadequate where the hides or the like being processed have very sharp bends or occasionally irregular shapes.
It should be also considered that a malfunction, however occasional, of these guiding devices has higly harmful consequences because it not only requires again an action from an operator but also that the guiding devices themselves be deactivated and the completed work be corrected. This to the point that in many cases the conventional guiding devices, even where available, are not used and manual supervision by the operators is used instead.